In the bowl of a stand mixer, mix together butter and sugar until light and fluffy.

Slowly add in eggs, one at a time, mixing until each egg is incorporated and scraping down the bowl in between additions.

Mix in the vanilla.

Add in 1/3 of the flour mixture on low speed, only until incorporated. Then add in 1/2 of sour cream. Mix until just combined. Alternate adding in flour and sour cream to the batter, ending with the flour. Ensure there are no lumps.

Once incorporated, gently fold in the melted chocolate.

Pour the batter into the bundt pan until it is approximately 3/4 full.

Bake in the oven for about an hour at 325F or until a toothpick inserted into the cake comes out clean.

Cool cake upright in the pan on a wire rack for about 15 minutes.

To make the glaze: Combine the water and sugar in a small saucepan over low heat. Stir until the sugar is completely dissolved. Remove the pan from the heat and add in the chocolate liqueur.

Place a piece of waxed paper or parchment paper underneath the wire rack. Invert the pan onto the wire rack, removing the cake from the pan. Using a pastry brush, coat the warm cake with the glaze. Allow the cake to come to room temperature. Dust the cake with icing sugar just before serving.